Read the TSO and then read the description of RAIM other
accuracy monitoring software built into the unit.



--
James H. Macklin
ATP,CFI,A&P

"Will" wrote in message
...
|
| "John Theune" wrote in message
| news:Udo3g.5009$bU6.3635@trnddc06...
| I'm somewhat surprised that no one has mentioned that
both the Garmin
| and Lowrance units that I'm familiar with have a page
for satelitte
| signal strength. I've never felt the need to run thru
the 430/530 pages
| to find a similar page but would not be surprised to
find it buried in
| there somewhere. To answer the OP's question it's there
you just need
| to read the manual to find which sub-menu it's on. If
he's using a
| non-aviation unit then all bets are off but again I
would think it would
| be there somewhere. Also on the units I use regularly
the airplane icon
| flashs on the main display when the signal is lost ala a
pseudo RAIM
| indicator
|
| You are right all GPS software usually implements a
satellite signal page.
| It's not in any way shape or form what I asked for.
|
| I want the GPS to take all of the inputs for number of
satellites and signal
| strength and derive from that just two integers:
|
| 1) Number of feet/meters of horizontal accuracy, within
some confidence
| interval (e.g., 99.95%)
|
| 2) Number of feet/meters of vertical accuracy, within some
confidence
| interval (e.g., 99.95%)
|
| Those two numbers could become optional numbers for the
primary display.
| No one is forcing anyone to use them. If you want to
simply trust the
| instrument to give you a go-nogo decision, it's your life
and if you feel
| that is safe it's a free world (as long as you follow FAA
rules ) so be
| my guest.
|
| For my personal taste, I understand that a GPS display is
always an illusion
| subject to different levels of inaccuracy. I am
sensitive to the
| difference between a display that is showing me accuracy
to 10 ft, 100 ft,
| or 1000 ft. In the original posted example the GPS was
off target by more
| than 5000 ft. Nothing on the original display gave me
any clue that this
| was the case. The two numbers I am asking for would
communicate quite
| succinctly that no one should rely on the display for
anything other than
| the most gross kind of positioning.
|
| While I would love to see the feature I am looking for in
any FAA-compliant
| instrument like a Garmin 530, I think the feature becomes
most critical in
| non-FAA compliant GPS devices/software. The authors of
such packages
| cannot control the quality of the satellite antenna, or
mounting, and
| substandard GPS reception is probably a routine thing for
PDA based GPS
| devices/software. So finding a succinct way to
communicate the accuracy of
| the current signal in numbers that mean something to any
user becomes quite
| important. Making people look at satellite maps and
signal strength seems
| like a pure engineering exercise, and it doesn't collapse
the input data
| into a useful form.
|
| --
| Will
|
|
|
|